The present application is based on and claims priority to Japanese Patent Application No. 2000-027,302, which was filed on Jan. 31, 2000, the entire contents of which are hereby expressly incorporated by reference.
1. Field of the Invention
The present invention generally relates to a lubrication system of an internal combustion engine. More particularly, the present invention relates to a lubrication system of a small watercraft engine that powers a water propulsion device.
2. Description of Related Art
As personal watercraft have become popular, they have become increasingly fast. Today, personal watercrafts are capable of speeds greater than 60 mph. To attain such speeds, personal watercrafts are driven by high power output motors.
Typically, two-cycle engines are used in personal watercraft because two-cycle engines have a fairly high power to weight ratio. One disadvantage of two-cycle engines, however, is that they produce relatively high emissions. In particular, large amounts of carbon monoxide and hydrocarbons are produced during operation of the engine. When steps are taken to reduce these emissions, other undesirable consequences typically result, such as an increase in the weight of the engine, the cost of manufacture, and/or the reduction of power.
It has been suggested that four-cycle engines replace two-cycle engines in personal watercraft. Four-cycle engines typically produce less hydrocarbon emissions than two-cycle engines while still producing a relatively high power output. However, adapting four-cycle engines for use in personal watercraft has its own engineering and technical challenges due to, at least in part, the limited space available within the hull of a personal watercraft.
A four-cycle engine utilizes a more complex lubrication system as compared with a two-cycle engine. In a four-cycle engine, a reservoir of oil is held in an oil pan below the crankcase to be available for circulation by an oil pump. One approach to enabling the use of a four-cycle engine in personal watercraft applications is to provide the engine with a dry sump lubrication system. A dry sump system utilizes a shallow reservoir of oil available for the oil pump as compared with the volume of oil in a wet sump system having an oil pan, thus reducing the overall height of the engine. One drawback in a dry sump lubrication system is that rapid changes in acceleration of the watercraft may cause shifting of oil away from the oil pump inlet such that oil is temporarily unavailable for the oil pump. The occurrence of such a condition reduces the effectiveness of the lubrication system.
Thus, there exists a need for a dry sump lubrication system that ensures sufficient oil is readily available for the oil pump despite maneuvering of the watercraft.
Accordingly, in one aspect of the present invention, a watercraft comprises a hull defining an engine compartment. An internal combustion engine is supported within the engine compartment. The engine includes an engine body, which defines at least one cylinder bore therein. The engine body additionally defines a crankcase having a crankshaft rotatably supported therein. At least one oil cover is connected to the engine body and defines an oil cavity between the oil cover and crankcase. At least one oil gallery is defined within the engine body. An oil pump is configured to circulate oil between the oil cavity and the oil gallery. The oil pump has an inlet configured to draw oil from the oil cavity at a position toward a rear end of the engine. The oil cover includes at least one baffle configured to impede a flow of oil in a forward direction away from the oil pump inlet.
According to another aspect of the present invention, an internal combustion engine includes an engine body that defines at least one cylinder bore therein. The engine body additionally defines a crankcase having a crankshaft rotatably supported therein. At least one oil cover is connected to the engine body and defines an oil cavity between the oil cover and the crankcase. At least one oil gallery is defined within the engine body. An oil pump is configured to circulate oil between the oil cavity and the oil gallery. The oil pump has an inlet configured to draw oil from the oil cavity. The oil cover includes at least one baffle configured to impede a flow of oil in a direction away from the oil pump inlet.
According to an additional aspect of the present invention a small watercraft is includes a hull defining an engine compartment. An internal combustion engine is supported within the engine compartment. The engine has an engine body which defines at least one cylinder bore therein. The engine body is comprised of at least a first and second member with the first and second member being connected by at least one bolt. The bolt has a bolt head disposed within a countersink portion of the engine body. A plug substantially sealing the bolt head is disposed at least partially within the countersink portion. An oil cover comprises at least one projection that is at least partially disposed above the plug.
Further objects, features and advantages of the present invention over the prior art will become apparent from the detailed description of the drawings which follows, when considered with the attached figures.